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White Clawed CrayfishThe white-clawed crayfish is Britain’s only native crayfish species and is our largest freshwater invertebrate, growing up to 12cm in length. It is found in rivers and streams throughout Europe, but has declined dramatically over recent decades. Threats to the white-clawed crayfish include changes to habitat and water quality, pollution and the introduction of non-native crayfish species in particular the American signal crayfish which was originally farmed for food in the UK. The signal crayfish is bigger and more aggressive than the white-clawed crayfish therefore can out compete for food. LegislationThe white-clawed crayfish is protected under Appendix III of the Bern Convention, Annexes II and V of the EC Habitats Directive and is classed as Globally Threatened by IUCN/WCMC . It is also protected under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended) which prohibits the taking of any native crayfish for any purpose except under licence. The Import of Live Fish Act also protects the white-clawed crayfish through the Prohibition of Keeping Live Fish (Crayfish) Order 1996. The UK Biodiversity Action Plan lists the white-clawed crayfish as a priority species and an action plan has been prepared to encourage measures for its survival. The populations in Britain represent the greatest concentration of the species in Europe (Holdich, 2003). SurveyThe suitability of a habitat can be assessed at any time of year, although the actual survey season is quite restricted and short (April and July to October). Hand searching during the day and/or torch survey at night when water flow rates are low, are the most commonly used techniques, although crayfish trapping is also effective. |
